Electric-arc lamp



UNITED STATES PATENT ()FFICE.

LOUIS E. HOWARD, OF PLAINFIELD, NEW JERSEY.

ELECTRIC-ARC LAMP.

SPECIFICATION forming part of Letters Patent No. 503,539, dated August 15, 1893.

Application filed June 9, 1893. SerialNo. 477,036. (No model.)

To aZZ whom it may concern.-

Be it known that I, LOUIS E. HOWARD, a citizen of the United States, residing in Plainfield, in the county of Union and State of New Jersey, have invented certain new and useful Improvements in Electric-Arc Lamps, of which the following is a specification.

This invention relates to electric arc lamps.

Its object is to increase the life of the carbons, improve the quality of light, and to increase the efficiency of the lamp and render it operative with a lower voltage.

In carrying out my invention I surround the arc with a transparent or translucent heat resisting envelope tightly closed at all points below the arc, and provided with means for permitting the egress of heated gases at the top, and make this envelope sufliciently small in size so that the gases surrounding the arc may be maintained by the heat thereof in a luminous or incandescent condition. In on der to permit the feed of the upper carbon, an opening is made in the envelope suiticiently close in fit to just permit of the feed, and the arc is located near the top of the inclosing envelope for the purpose of preventing a waste of the positive carbon and preventing the ingress of air through the feed opening. It has heretofore been proposed to inclose the arc in an air-tight envelope, but all such efforts have so far as I am aware resulted in failure. If, as has been the case, the inclosing envelope is made comparatively largein diameter, say, five inches or upward, it is impossible to maintain the gases in aluminous or incandescent condition, and if the opening through which the carbon feeds is made sufficiently large to admit of very free transit of the carbon through itingress of air is permitted which increases the rapidity of consumption of the carbons; moreover, where the lamp is exposed to the elements, rain or a draft of cold air striking the containing chamber when made of glass is apt to shatter it. With my construction these difficulties are overcome. I am enabled to make the transparent or translucent inclosing envelope three inches in diameter, a size which will admit of maintaining the gases around the arc incandescent or opalescent, resulting in an agreeable light of large radiating area; and

by making the feed opening a comparatively close fit around the carbon and providing a valve or trap for the escape of heated gases when the tension becomes sufficient to endanger the envelope, the life of the carbon is prolonged to an extraordinary degree. A further incident of great importance which follows from the reduction in size of the inclosing envelope is that the lamp will operate at a lower voltage than other types of arc lamps, a result probably due to an increased degree of conductivity of the are because of greater density of the hot gases.

The several features of novelty of the invention will be more particularly hereinafter described and will be definitely indicated in the claims appended to this specification.

In the accompanying drawings which illustrate the invention, Figure 1 represents an arc lamp constructed in accordance with my invention; and Figs. 2 and 3 are detail views of the plug used at the top of the arc-inclosing envelope through which the carbon is fed, and which is provided with means for permitting an egress of the heated gases,

Where the lamp is exposed to the action of the elements an auxiliary globe A will be provided around the arc-inclosing envelope to prevent rain or drafts from striking its highly heated surface.

The feed-regulating mechanism may be of any suitable construction, and as it forms no part of my present invention need not be specifically described.

Surrounding the arc is a transparent or translucent envelope B preferably made of glass, and not to exceed three inches, and preferably less, in horizontal diameter and of any desired length. This chamber is formed of substantially a bottle shape,having a neck at the top and is open at the bottom. At the bottom edge is formed by molding or otherwise a screw thread 0, and a metal cap D provided with a socket for the negative carbon E is provided with a cooperating thread forming a close fit which when screwed upon the bottom of the envelope B with an interposed washer of asbestos will form a gas-tight joint. This cap may be spun from a metal capable of withstanding comparatively high temperatures, such as copper or an alloy, and thesocket is formed integral therewith or attached in any suitable manner so as to form a gas proof and heat resistant joint. The are is located near the top of the inclosing envelope, and the neck is provided with a fireproof plug F formed of asbestus pulp or any other suitable material into which screws a metal plug G formed of two parts, as seen at g, 9', Fig, 2, between which may be clamped a washer of soft heat-resistance material, such as asbestus, indicated at 9 By this means a comparatively close fit may be formed around the positive carbon H, the asbestus washer g yielding sufficiently although a comparatively close fit to permit an easy feed of the positive carbon H. Through the body of the plug G is formed an opening I over which rests a hinged metal valve J provided with a limiting stop K.

WVith this construction the'operation of the lamp will be as follows: Upon the closure of the circuit and the springing of the arc the air in the inclosing envelope B is robbed of its oxygen, and after a short time the entire body of the gas chamber B becomes highly posited on the negative electrode and serve to build up said electrode and maintain the are substantially stationary in position, or in any event at a point above the horizontal center of the envelope B and above the heavier gases which collect at the bottom of the envelope, while a very slow destruction of the positive electrode proceeds. In time a light deposit will be formed upon the inner wall of the envelope B, but the heat of the inclosed gases when this envelope is of substantially the size specified is sufficient to maintain this deposit in an incandescent or opalescent condition,adding to the effectiveness of the light and the rapidity with which the highly luminous condition is effected. It

is important that the plug G surrounding the positive electrode should be metallic as it will then by reason of its high conductivity maintain the tension of the thin film of gas around the carbon in the feed opening and better prevent the ingress of the cold outside air. It is, moreover, important that the metal should not come into direct contact with the glass inclosing envelope B, when the latter is made of that material, in order to prevent fracture, and it is for this reason that some heatnon-conducting and fire-proof substance such as asbestus is interposed. It is, moreover, important that the arc should be formed near the top of the inclosing envelope since when so located it willlocalize the heat at the top of the chamber and the better prevent the ingress of air byincreasing the tension of the inclosed gases at that point, thus conserving the life of the carbons; moreover, when so located but a short length of the positive carbon will be exposed to the high heat of the arc and. surrounding gaseous envelope, thus lowering the temperature of the external portion of the positive carbon and reducing the amount of disintegration. Besides this, carbon when exposed to a high heatis subject to a process of over-carbonization,lby which it becomes comparatively porous and its resistance is increased. By exposing only a short section of the positive carbon such over-carbonizatlon is limited in extent and the resistance of the lamp is therefore lower than it would be if the arc were maintained lower in the inclosing envelope. Another incident resulting from the location of the are near the top of the envelope is the maintenance of steadiness and a maximum angle of illumination. I have observed, moreover, that when so located there is less liability of the bead formed on the negative electrode by the transit of carbon across the are to break off, and a smoother surface of the negative carbon is presented to the arc and a more equable action of the lamp maintained. Accurate tests indicate that a lamp of my construction as hereinbefore described will require only twenty-five or thirty volts for, its operation, as contrasted with forty-five or fifty volts in other types of lamps. I attribute this result to the dense body of conducting gas maintained in close relation to the are by which its resistance is materially lowered and the Voltage necessary to maintain its action is reduced. The small arc-inclosing envelope prevents dissipation of the gases and maintains them at a greater density than would be possible with a large envelope. Besides conserving the energy in the manner already described the gases glow with increased brilliancy by reason of the greater density.

In operating with my lamp'I find that the best results are obtained by using absolutely pure carbons, and I find thatthenegative carbon is increased in length or held above the center of the envelope B, whereas the positive carbon is so slowly consumed that a carbon of less than twelve inches in length will maintain the arc and its gaseous envelope in continuous operation for more than one hundredhours with a consumption of two hundred and seventy watts, as contrasted with a life of seven hours and a consumption of five hundred to six hundred watts with other forms of arc lamps.

I am aware that it has been proposed heretofore to operate an arc lamp in an air-tight envelope, but when the envelopes are sealed an explosion of the cylinder is liable to result, and when not sealed, a rapid consumption of carbons will result and a smoking of the inclosing envelope. Valves which rely for their action upon accumulated pressure will interfere with a good action of the lamp and make the light fluctuate in intensity and cause sputtering. In my lamp, however, the inclosure, although practically tight against ingress of air, allows a steady outflow of gases from the lamp. By means of my construction I provide as hereinbefore stated a light of large radiating surface which is far more desirable as 'a source of illumination than one in which the light is emitted from a center of small surface such as an ordinary arc.

hat I claim as my invention is 1. An arc lamp having the electrodes around the arc inclosed in a small transparent or translucent envelope air-tight at all points below the arc and provided With a normally closed valve above the arc whereby the envelope is filled with a highly luminous gas and the life of the electrodes is prolonged.

2. An arc lamp having its electrodes around the arc inclosed in a small transparent or translucent envelope so arranged as to maintain the gases luminous in said envelope and air-tight against ingress of air but affording egress for the heated gases developed by the arc.

3. An arc lamp having its electrodes around the arc inclosed in a transparent or translucent envelope air-tight at all points below the are, so arranged as to maintain the gases luminous in said envelope said are being located near the top of the envelope, means for preventing the ingress of air, and an outwardly opening valve for permitting the discharge of gases.

4. An arc lamp having its arc inclosed in a small transparent or translucent envelope closed air-tight below the arc, so arranged as to maintain the gases luminous in said envelope a closely fitting opening to permit feed of the positive carbon, and an outwardly opening normally closed valve in the top of the envelope adjacent to the heated gases.

5. An arc lamp having its arc inclosed in a transparent or translucent envelope provided with a metallic plug having a closely fitting opening to permit feed of the positive carbon and means for permitting escape of the gases produced by the arc. r

6. An arc lamp having its arc inclosed in a transparent or translucent envelope closed air-tight at all points below the arc, and provided with a plug at the top having a closely fitting feed opening for the positive carbon.

7. An arc lamp having its arc inclosed 111 a transparent or translucent envelope closed air-tight at all points below the are, a plug in the top of the envelope provided w th a closely fitting feed opening for the positive carbon, and a valved opening in said plug.

8. An arc lamp having its arc inclosed in a transparent or translucent envelope closed air-tight at all points below the are, a closely fitting opening in the top of the envelope to permit feed of the positive carbon, and a heat non-conducting wall between the wall of the envelope and the feed opening.

9. An arc lamp having its arc inclosed in a transparent or translucent envelope closed air tight at all points below the are, a plug 111 the envelope above the are provided w th a closely fitting feed opening for the posit ve carbon, and an outwardly opening gravity valve normally closing a vent for the gases developed by the arc.

10. An arc lamp having its arc inclosed in a transparent or translucent envelope closed air-tight at all points below the arc, a metallic plug in the top of the envelope provided with a feed opening for the positive carbon, and an annular lining of yielding fire-proof material such as asbestus producing a closely fitting wall around the carbon.

11. An arc lamp having its arc inclosed in a glass envelope provided with a closely fitting feed opening for the positive carbon at the top, and a gas-tight metallic cup provided with a threaded rim engaging a thread on the bottom of the glass envelope, said cup having a metallic socket for the negative carbon.

In testimony whereof I have hereunto subscribed my name this the 8th day of June,

LOUIS E. HOWARD. Witnesses:

RoB'r. I-I. READ, E. O. GRIGG. 

